The bracing assembly of this invention is believed to have primary utility in regeneration vessels of fluid catalytic cracking units because the physical conditions present within such units are extremely severe. Operating temperatures may be as high as around 1450.degree. F. in some regions in the unit and as low as about 1150.degree. F. in other portions while the vessel shell temperature is only 300.degree.-350.degree. F. Moreover, in the case of an upset in operations rapid temperature changes can occur within the unit. Also the cyclone diplegs are subjected to the mechanical forces of particulate catalyst bed motion created by bursting bubbles of combustion gases which can result from normal or damaged air rings or spargers. Regeneration vessels are usually constructed to be quite tall in order to accommodate the catalyst dense bed and an adequate dilute phase (disengaging) zone above the bed. Since the cyclones are supported at the top of the vessel and the diplegs extend into the dense bed it is necessary that the diplegs be quite long relative to their diameters. Thus, it is desirable to provide bracing to prevent motion of the lower ends of the diplegs but heretofore this has been difficult to accomplish in some designs because intolerable thermal stresses can develop due to temperature changes and differentials which inevitably occur.
U.S. Pat. No. 4,273,565 to Worley discloses a cyclone support system suitable for use in a fluid coke burner. In this unit a number of cyclones are rigidly attached to the top of the vessel and the lower portions of adjacent diplegs are connected by horizontal bars apparently welded to the diplegs. The Worley arrangement, however, is not suitable for use in a fluid catalytic cracker regenerator unit, because wide temperature differentials can exist between the top of the vessel where the cyclones are attached and the region near the bottom of the vessel where lower ends of the diplegs are located. This temperature differential, if fixed braces are employed, will create high stresses leading to failure and requiring unit shutdown.
It is accordingly an object of this invention to provide a bracing assembly which will support a plurality of cyclone diplegs to minimize swaying and bending of the diplegs without the development of high thermal stresses.
It is a further object to provide an arrangement whereby each of a plurality of diplegs arranged in a polygonal pattern serves to provide bracing for the other diplegs.